This disclosure is related to the field of systems for spray application of multiple component liquid compounds, wherein the multiple components are mixed at the point of spray application. More specifically, the disclosure relates to systems for such spray application which require very precise control over the volume and/or mass flow rate of each of a plurality of liquid chemicals when applied by a spray gun.
Spraying systems known in the art for application of multiple component liquid chemicals known in the art include reciprocating-type pumps having inlets disposed in standard sized containers, e.g., 55 gallon drums. The reciprocating pumps are selectively actuated to move each of a plurality of liquid chemicals through respective hoses to a spray application “gun” or sprayer, wherein the plurality of liquid chemicals is mixed at the point of application of the spray discharged from the sprayer. Discharge from the pumps is conducted to the spray gun through respective hoses. Such systems may or may not include a separate hose for introduction of gas under pressure, such as air, to help atomize the liquid chemicals for spray application. Examples of such multiple component liquid chemicals include thermal insulation which may consist of two liquid components to be mixed at the point of application. The two liquid components react at the point of application to form a foam, which eventually cures into finished insulation.
Manufacturers of multiple component liquid chemical compounds specify the volume and/or mass of each component that is required to be dispensed so that the correct chemical reaction or other physical process (e.g., evaporation) takes place at the point of application. Using systems known in the art for spray applying multiple component chemicals may not have sufficient accuracy in determining the volume and/or mass flow rate of each component chemical to dispense the manufacturer-specified amount of each component chemical when the spray is actually applied.
Systems known in the art may also allow environmental and personnel hazards resulting from use of chemical withdrawn from open containers, and from the users being required to transfer the pump inlets from empty chemical containers to full ones when containers are emptied. The former limitation of systems known in the art results from the temperature of the sprayed component chemicals being uncontrolled, and from lack of accuracy in measurement of volume and/or mass of each liquid component actually moved by reciprocating-type liquid pumps. A further environmental exposure may result from the need to dispose of empty liquid containers. Some liquid chemicals may be reactive with ambient air, and as a result using containers that are exposed to the air when opened may enable degrading of such reactive chemicals.